refactor: replace authentication field with envVars in TPMJS specification

Replace the authentication field with a more general envVars array that allows tools to specify required environment variables:

Changes to type definitions:
- Remove TpmjsAuthenticationSchema and TpmjsAuthentication type
- Add TpmjsEnvVarSchema with fields: name, description, required, default
- Replace authentication field with envVars array in TpmjsRichSchema
- Update validateTpmjsField to check envVars instead of authentication

Changes to documentation:
- Update /spec page to document envVars instead of authentication
- Update /publish page examples to use envVars
- Update HOW_TO_PUBLISH_A_TOOL.md with envVars examples
- Update validation errors section
- Remove authentication from @tpmjs/createblogpost example

The envVars field is more flexible and clearer - it lists all environment variables a tool needs (API keys, endpoints, config values) rather than trying to categorize authentication types.

Example:
```json
"envVars": [
  {
    "name": "OPENAI_API_KEY",
    "description": "API key for OpenAI services",
    "required": true
  }
]
```

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

packages/tools/createBlogPost/package.json

@@ -80,10 +80,6 @@
       "type": "BlogPost",
       "description": "A structured blog post object with frontmatter, content, and metadata including slug, wordCount, readingTime, and formattedOutput"
     },
-    "authentication": {
-      "required": false,
-      "type": "api-key"
-    },
     "frameworks": ["vercel-ai", "langchain"],
     "links": {
       "documentation": "https://tpmjs.com/tools/createblogpost",

packages/types/src/tpmjs.ts

@@ -44,16 +44,16 @@ export const TpmjsReturnsSchema = z.object({
 export type TpmjsReturns = z.infer<typeof TpmjsReturnsSchema>;
 
 /**
- * Authentication configuration schema
+ * Environment variable schema
  */
-export const TpmjsAuthenticationSchema = z.object({
-  required: z.boolean(),
-  type: z.enum(['api-key', 'oauth', 'basic-auth', 'custom']),
-  envVar: z.string().optional(),
-  docsUrl: z.string().url().optional(),
+export const TpmjsEnvVarSchema = z.object({
+  name: z.string().min(1),
+  description: z.string().min(1),
+  required: z.boolean().default(true),
+  default: z.string().optional(),
 });
 
-export type TpmjsAuthentication = z.infer<typeof TpmjsAuthenticationSchema>;
+export type TpmjsEnvVar = z.infer<typeof TpmjsEnvVarSchema>;
 
 /**
  * External links schema
@@ -99,7 +99,7 @@ export type TpmjsMinimal = z.infer<typeof TpmjsMinimalSchema>;
 export const TpmjsRichSchema = TpmjsMinimalSchema.extend({
   parameters: z.array(TpmjsParameterSchema).optional(),
   returns: TpmjsReturnsSchema.optional(),
-  authentication: TpmjsAuthenticationSchema.optional(),
+  envVars: z.array(TpmjsEnvVarSchema).optional(),
   frameworks: z
     .array(z.enum(['vercel-ai', 'langchain', 'llamaindex', 'haystack', 'semantic-kernel']))
     .optional(),
@@ -138,7 +138,7 @@ export function validateTpmjsField(tpmjs: unknown): ValidationResult {
     const hasRichFields =
       data.parameters ||
       data.returns ||
-      data.authentication ||
+      data.envVars ||
       data.frameworks ||
       data.links ||
       data.tags ||